1. Field of the Invention
The present invention relates to sensors, and particularly to a method of making thin film humidity sensors having application in environmental monitoring, process control, food processing, storage and packaging.
2. Description of the Related Art
Because of the universal existence of water, the control of humidity is very essential, not only for human comfort, but also for manufacturing processes and industrial products. Humidity sensors are widely used in the semiconductor, automobile, medical, pharmaceutical, health care, textile, paper, agriculture and food industries.
Commercially available humidity sensors are fabricated by conventional sensing materials, such as alumina, ceramics, and electrolytic metal oxides. Depending upon the nature of materials, these sensors may be expensive or may require high operational power/temperature and high cost of maintenance. To make the sensor suitable for commercialization, wide range sensitivity, linear response, small hysteresis, short response and recovery time, low cost and low power, along with long-term physical and chemical stability, are the required characteristics. Presently, most of the humidity sensors used in research laboratories and industries are based on water-phase photonic ceramic materials. But, these ceramic-based sensors have problems of response and recovery time and sensitivity towards smoke and dust (contaminants).
Thus, a method of making thin film humidity sensors solving the aforementioned problems is desired.